Manufacture of tubular or hollow bodies from plastic materials.



i06- CUMIUSIIIUNS,"

COATING OR PLASTIC.

@MTED STATES PATENT OFFICE.

LOUIS HERMANN RENTZSCH, OF MEISSEN, GERMANY.

MANUFACTURE OF TUBULAR OR HOLLOW BODIES FROM PLASTIC MATERIALS.

. Hollow Bodies from Plastic Material, ofwhich the following is aspecification.

It is well known to manufacture hollow bodies from plastic mass byexposing it to dentrr uga Ron in a rotating mold, and on the other handit is well known to add fibrous substances of organic or inorganicorigin to the plastic material (cement or gypsum paste) used formanufacturing cast bodies, for the purpose of greater strengthening ofthe finished article. In attempts to combine these two well knownprocesses, that is to say, to manufacture hollow bodies from plasticmass with the addition of fibers, by centrifugal action, it has beenfound that, owing to the difference in the absolute weights the actionof centrifugal force was accompanied by the formation of layers whichmade it impossible to obtain in the finished work, a walluuiformlyprovided with fibers. This difficulty has been overcome byadding fibrous materials which have substantially the same absoluteweight as the plastic mass itself, in the state in which it settles onthe wall of the molds during the centrifugal action at which momentwater is separated from it. This condition is, however, seldom fulfilledby the substances that come under consideration. The easiest way toattain the desired result is to select suitable fibrous materials whengypsum paste or other plastic materials or masses of small specificgravity is employed. If necessary, the absolute weight of the fibrousmaterial must, therefore, be altered, as a rule, increased. This is donein the simplest manner by soaking it in water, but it can also beeffected by impregnating it with suitable heavy substances, for instancewith heavy metallic salts or silicates.

The impregnation of fibrous materials with substances dissolved in wateror other liquid, or, if they are insoluble, suspended in the saidliquids, has the advantage over weighting with simple water or simpleliquid, that the impregnated fibrous materials do not lose quite so muchin weight when they are subjected to pressure during the action ofcentrifugal force, for while pure water simply becomes separated fromthe fibers, on the contrary when a solution or a paste has been used,the greatest portion of the substances which were dissolved or suspendedin water, remains on the fibers. There takes place, therefore, aprecipitation of the substance in question on the fiber. 1

In cases in which the fibrous material, if completely saturated withwater, would become too heavy, the proper weighting can be effected byfirst impregnating the fibrous material until complete saturation, andthen Specification of Letters Patent.

Application filed December 1, 1906. Serial No. 345,954.

Patented Sept. 17, 1907.

removing a corresponding portion of the water in any suitable manner.

For the practical carrying out of the process, it is further necessaryto take into consideration the modification of the weight of theartificially weighted fibrous are brought into contact with the plasticmaterial, more water is absorbed or given off, or the weightingsubstance passes into solution. It is, therefore, an unstable value, andcare must be taken that the weight should be correct at the propermoment. The most important conditions are those obtaining at the momentat which the material is deposited on the Wall of the mold. For if theweight changes after that, that circumstance is of no importance, as thefibrous material becomes embedded after being deposited, and is heldfast mechanically, The fibrous materials must, therefore, be added tothe plastic mass at the proper moment before subjecting them tocentrifugal action. It is very difficult to give exact and definiteinstructions for the practical carrying out of the process according tothis invention, as the conditions differ in each individual case. After,however, the reason why the fibers become stratified, and thepossibility of avoiding such stratification by keeping the weightsequal, have been properly understood, it will be easy to apply theinvention to single cases in a proper manner. Nevertheless, as anexample for the practical application of this process, the manufactureof a tube from cement with asbestos fiber insertion will be described. 2kgs. of asbestos fibers are soaked in four liters of water, where a at amous paste is obtained whimoughly stirred. About a quarter of an hourafterwards the cement required for manufacturing the tube, about s. sadded to the said mass in the shape of a thick paste, and the two sub;stances are quickly, but thoroughly, stirred together. It is notadvisable toadd the cement in dry state, as in that case it would absorbwater from the asbestos, and thus render the fibrous material too light.The whole mass is then subjected for about half an hour to cenness ofwall is to be made), and then the mold is allowed to stand for about 48hours, until the mass becomes set, whereupfii the mold is opened and thefinished product withdrawn. Although it is preferably intended tomanufacture cylindrical pipes with walls of uniform thicknessthroughout, the hollow bodies round, that is to say, rectangular,square, polygonal or the like.

When manufacturing hollow bodies of cylindrical shape which must haveuniform thickness of walls in milimeters outside diameter and 10millimeters thick-.

could also be formed with outer surfaces which are not materials duringthe whole treatment, since, after they longitudinal direction, thecylindrical mold, as is well known, must be arranged horizontally. Ifthe axis of rotation of the mold were not horizontal, the plastic mass,due to its gravity, would sink to the points situated lower down, andform at those points a thicker wall than at the points situated higherup.

If it be desired to produce conical tubular bodies, then a horizontalposition of the axis of the rotating mold would form an obstacle to theformation of a uniform thickness of wall as the plastic material isdriven by centrifugal force to that side of the mold which has thelargest diameter. Whether this drawb tck becomes noticeable to a greateror lesser extent, depends both on the weight of the mass and on theangular speed with which the mold rotates, as well as on the angle whichthe casing of the mold forms with the axis of the mold. According tothis invention, uniform distribution of the material on the conical wallof the mold is obtained by arranging the axis of the mold obliquely. Theangular speed must of course be exactly determined so that the tendencyof the centrifugal force to press the mass towards one side of the moldwill be counteracted, that is so say, the tendency of the centrifugalforce to press the mass towards the side having the greater diameterwill naturally remain the same, but the action of the mass itself, underthe influence of its gravity, will equalize the action of thecentrifugal force by its tendency to press the mass towards the narrowerside situated at a lower level.

As the angular speed of the centrifugal apparatus is generally given,although in different adjustable degrees, the oblique position of theaxis of the mold corresponding to the given angular speed, must beascertained by calculation, which can be done in each individual casewithout any dilficulty. In addition to this method of utilizing theoblique position of the axis of the mold, it is of course, possible, bysuitably changing the oblique position of the axis, to obtain a onesidedstrengthening or thickening of the wall of the tube to be produced, andit is perfectly possible to make the increase of thickness in suchmanner as required for a given purpose.

What I claim as my invention and desire to secure by Letters Patent is:

'1. The process of manufacturing hollow bodies from plastic material,consisting in mixing with the plastic material fibrous material ofsubstantially the same absolute weight, and then subjecting the mass tocentrifugal action in a rotating mold.

2. The process of manufacturing hollow bodies from plastic materialconsisting in mixing with the plastic material, fibrous material whoseweight has previously been increased to that of the plastic material,and subjecting the mass to centrifugal action in a rotating inold.

3. The process of manufacturing hollow bodies from plastic material,consisting in mixing with the plastic material lighter fibrous materialwhose weight has been previously increased to the desired extent byimpregnation with weighting substances and subjecting the mass tocentrifugal action in a mold.

4. The process of manufacturing hollow bodies from plastic material,consisting in mixing with the plastic material lighter fibrous materialwhose weight has previously been increased to the desired extent bysoaking in water, and subjecting the mass to centrifugal action in amold.

5. The process of manufacturing hollow bodies from plastic materialconsisting in mixing with the plastic material, asbestos fiberpreviously saturated with water to increase its weight, and thensubjecting the mass to centrifugal action in a mold.

6. The process of manufacturing hollow bodies from cement paste,consisting in mixing with the paste asbestos fiber previously saturatedwith water, and then subjecting the mass to centrifugal action in amold.

7. The process of manufacturing conical hollow bodies from plasticmaterial consisting in mixing fibrous material In testimony whereof Ihave signed my name to this specification in the presence of twosubscribing winesses.

LOUIS HERMANN RENTZSCH.

Witnesses:

0TH. VOEN, RICHARD G. WEBKE.

